179 
Potamogetonaceæ. 
Determ. J. Baagøe, Næstved, Denmark. 
1. Potamogeton. 
1. P. nodosus Poir. P. fluitans Roth. 
Roth’s name is from 1788 and elder than Poiret’s name, which 
is from 1816; I have used the latter 1 ), because some botanists consider 
the steril hybrid P. lucens X natans as Roth’s plant, others the 
fructiferous and again others (Ascherson und Graebner Syn. Mitteleur. 
Flora 1897) refer both the hybrid and the fructiferous „ P.fluita?is u 
to the same species. This is not at all correct, these two forms 
diverge in several respects. Original fructiferous specimens of Roth’s 
P. fluitans I have seen in the herbarium of St. Petersburg, but Roth 
has in his describing the plant in Tent. Fl. Germ. I. (1788) 72 
. . . foliis inferioribus longissimis“ and in Tent. Fl. Germ. II 
(1789) 202 „. folia inferiora pedalia et longiora“ no doubt 
had the hybrid before him (the above mentioned character is parti- 
culary characteristic for the hybrid, while the fructiferous plant 
has short submerged leaves); perhaps Roth has emitted both plants 
under the same name, and until it can be fixed, which plant shall 
bear Roth’s name, or whether this is to be retained after all, I 
will use the name given by the author, who is next after him, 
viz. P. nodosus Poir. (P. occidentalis Sieb., P. canariensis Link, 
P. americanus Cham. and more are of later date). 
N. 1951. Chiwa, in a pond. July 11. 1899. 
N. 1980. Chiwa, in a pond by Chasawat. July 15. 1899. 
J ) Proposed by Mr. O. Hagstrom (Lyswik, Sweden). 
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